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Background: Staphylococcus aureus dominates the lung microbiota of children with cystic fibrosis (CF) and persistent clones are able to establish chronic infection for years, having a direct deleterious impact on lung function. However, in this context, the exact contribution of S. aureus to the decline in respiratory function in children with CF is not elucidated.Methods: To investigate the contribution of persistent S. aureus clones in CF disease, we undertook the analysis of sequential isogenic isolates recovered from 15 young CF patients.Results: Using an air-liquid infection model, we observed a strong correlation between S. aureus adaption in the lung (late isolates), low toxicity, and proinflammatory cytokine secretion. Conversely, early isolates appeared to be highly cytotoxic but did not promote cytokine secretion. We found that cytokine secretion was dependent on staphylococcal protein A (Spa), which was selectively expressed in late compared to early isolates as a consequence of dysfunctional agr quorum-sensing system. Finally, we demonstrated the involvement of TNF-α receptor 1 signaling in the inflammatory response of airway epithelial cells to these lung-adapted S. aureus isolates.Conclusions: Our results suggest an unexpected direct role of bacterial lung adaptation in the progression of chronic lung disease by promoting a proinflammatory response through acquired agr dysfunction. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus is a leading cause of both acute and chronic infections in humans. The importance of the pentose phosphate pathway (PPP) during S. aureus infection is currently largely unexplored. In the current study, we focused on one key PPP enzyme, transketolase (TKT). We showed that inactivation of the unique gene encoding TKT activity in S. aureus USA300 (∆tkt) led to drastic metabolomic changes. Using time-lapse video imaging and mice infection, we observed a major defect of the ∆tkt strain compared with wild-type strain in early intracellular proliferation and in the ability to colonize kidneys. Transcriptional activity of the 2 master regulators sigma B and RpiRc was drastically reduced in the ∆tkt mutant during host cells invasion. The concomitant increased RNAIII transcription suggests that TKT-or a functional PPP-strongly influences the ability of S. aureus to proliferate within host cells by modulating key transcriptional regulators. [ABSTRACT FROM AUTHOR]

Background Chronic lung infection in cystic fibrosis (CF) patients by Staphylococcus aureus is a well-established epidemiological fact. Indeed, S. aureus is the most commonly identified pathogen in the lungs of CF patients. Improving our understanding of the mechanisms associated with the persistence of S. aureus is therefore an important issue. Methods We selected pairs of sequential S. aureus isolates from 3 patients with CF and from 1 patient with non-CF chronic lung disease. We used a combination of genomic, proteomic, and metabolomic approaches with functional assays for in-depth characterization of S. aureus long-term persistence. Results In this study, we show that late S. aureus isolates from CF patients have an increased ability for intracellular survival in CF bronchial epithelial-F508del cells compared to ancestral early isolates. Importantly, the increased ability to persist intracellularly was confirmed for S. aureus isolates within the own-patient F508del epithelial cells. An increased ability to form biofilm was also demonstrated. Furthermore, we identified the underlying genetic modifications that induce altered protein expression profiles and notable metabolic changes. These modifications affect several metabolic pathways and virulence regulators that could constitute therapeutic targets. Conclusions Our results strongly suggest that the intracellular environment might constitute an important niche of persistence and relapse necessitating adapted antibiotic treatments. [ABSTRACT FROM AUTHOR]

Purpura fulminans (PF) is a dreadful and frequent complication of Neisseria meningitidis invasive infection, and is associated with a high mortality rate. This syndrome begins with dermal microvessels thrombosis that rapidly lead to hemorrhagic skin necrosis. In this review, we discuss the prothrombotic events occurring during meningococcal infection. Moreover, recent data from an experimental mouse model have highlighted the critical role of the meningococcus adhesion to the endothelium in the development of PF lesions, thus opening new therapeutic perspectives. [ABSTRACT FROM AUTHOR]

Neisseria meningitidis is a strict human pathogen that closely interacts with human endothelial cells via type IV pili in vitro. To decipher whether this interaction plays a role in vivo, we set up an experimental model of fulminant meningococcemia in human skin grafted SCID mice using the wild-type strain 2C4.3. Human skin and mouse tissues were sampled 24 hours after bacterial challenge for histopathology, immunohistochemistry and ultrastructural analysis. In all infected mice, N. meningitidis targeted the human vasculature, leading to bacterial and blood thrombi, infectious vasculitis and vascular leakage. Mouse vessels, including brain vessels, remained unaffected by the infectious and thrombotic process, and a nonpiliated Δ pilE derivative of 2C4.3 failed to target human graft vessels and to induce vascular damages. These data demonstrate that N. meningitidis targets human endothelial cells in vivo and that this interaction triggers the vascular damages that characterize purpura fulminans. [ABSTRACT FROM AUTHOR]

Chronic meningococcemia is a form of sepsis with frequent polymorphous skin lesions. Both in vivo and in vitro data suggest that, in these lesions, meningococci gain access from the capillary lumen to the peripheral extravascular compartment, in the absence of vascular dislocation, through a paraendothelial route. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Bone Marrow-Derived Stem Cells Do Not Reconstitute Spermatogenesis In Vivo," published in the previous issue.